Textile materials are typically dyed with an aqueous dye liquor. In such techniques, a complete bath exhaustion rarely occurs: that is, the dyes do not exhaust quantitatively onto the respective substrate. Thus, after the dyeing process, the residual dye liquor may still contain a large amount of dye. As a result, dyeing produces large amounts of colored effluents which must be purified at considerable time and expense.
The dyeing of substrate materials in liquid or supercritical CO.sub.2 has been disclosed. See, e.g., A. Clifford and K. Bartle, Textile Technology International, 113 (1995); U.S. Pat. No. 5,578,088 to Schrell et al.; U.S. Pat. No. 5,512,058 to Gavend et al.; U.S. Pat. No. 5,298,032 to Schlenker et al.; U.S. Pat. No. 5,250,078 to Saus et al.; U.S. Pat. No. 5,199,956 to Schlenker et al.; and German Offenlegungschrift DE 4429470A1.
Processes for carbon dioxide dyeing currently available are not entirely satisfactory, and there is a continued need for new ways to carry out the dyeing of substrates in carbon dioxide.